1. Technical Field
The present invention relates generally to the field of power generation and more specifically relates to systems and methods for creating energy from naturally occurring events and conditions.
2. Background Art
Ocean waves provide a significant and largely untapped potential energy resource. Research in this area is driven by the need to meet renewable energy targets, but is relatively immature compared to other renewable energy technologies such as solar and wind power. Although solar and wind power have been studied for decades, with increasingly widespread adoption, the field of wave energy conversion is still considered a relatively new area of research and development.
In spite of the relative novelty of the field, the promise of energy from the oceans is significant. For example, the global wave power resource in deep water (e.g., greater than 50 m) is estimated to be about 26,000 TWh/year, which is the same order of magnitude as the electricity consumption for the entire world in 2007. Many scientists now recognize that using waves as a source of renewable energy offers significant advantages over other methods of energy generation including the following:                sea waves offer the highest energy density among all known renewable energy sources;        relatively minor negative environmental impact for the to amount of energy produced;        the natural seasonal variability of wave energy tends to roughly correlate with the electricity demand in temperate climates; and        waves can travel large distances with little energy loss.        
Given the many benefits associated with extracting energy from waves, there have been many previous attempts to create efficient and effective devices to create electrical energy from wave motion. There are many experimental wave-energy devices and much effort has been conducted to increase the efficiency of wave-energy devices. However, there is no large scale use of wave energy convertors (“WEC”) currently being used in the world today.
While use of wave energy conversion technology is highly desirable, there remains a number of technical challenges that need to be overcome to increase the performance and the commercial competitiveness of WEC in the global energy market. For example, it is rather difficult to convert the relatively slow (˜0.1 Hz), random, and high-force oscillatory motion produced by a series of waves into useful motion to drive a generator with output quality acceptable to the attached utility network. Given that waves vary in height and period, their respective power levels vary accordingly. While gross average power levels can be predicted in advance, this variable input has to be converted into smooth electrical output and, accordingly, usually necessitates some type of energy storage system, or other means of compensation such as an array of devices.
Similarly, in many offshore locations, wave direction is highly variable, and so wave devices generally need to be aligned accordingly on compliant moorings, or be symmetrical, in order to capture the energy of the wave. The directions of waves near the shore can be largely determined in advance owing to the natural phenomena of refraction and reflection but the difficulty associated with accurately estimating and understanding wave patterns is not a small matter.
Additionally, the challenge of efficiently capturing the relatively irregular motion associated with waves has also had an impact on the design of the device. To operate efficiently, the device and corresponding systems have to be rated for the most common wave power levels. However, the device also has to withstand extreme wave conditions that occur very rarely, but could have power levels in excess of 2000 kW per frontal meter. Not only does this pose difficult structural engineering challenges, but it also presents one of the economic challenges as the normal output of the device (and associated revenue) are produced by the most commonly occurring waves, yet the capital cost of the device construction is driven by a need to withstand the high power level of the extreme, yet infrequent, waves. There are also additional design challenges that must be overcome in order to mitigate the highly corrosive environment of devices operating in or near seawater.
Finally, although many experimental and early stage wave energy extraction projects hold some promise, there yet remains a lack of convergence on the best method of extracting energy from the waves and, although previous innovation has generally focused on the concept and design of the primary interface, questions arise concerning how best to optimize the components of the systems, including the generation mechanism and the associated powertrain and energy transfer mechanisms. Accordingly, without additional developments and improvement in the practical application of floating bodies and PTO systems, the extraction of available energy from ocean waves will continue to be suboptimal.